Core wrapping method and apparatus



Dec. 13, 1960 Filed Sept. 2, 1954 C. E. NIXON CORE WRAPPING METHOD ANDAPPARATUS @L VE I 5 Sheets-Sheet 1 Eur a suaw INVENTOR 6 17/4/9455 5/V/X0/V BY 63425, H w in/M ATTO R N EY5 Dec. 13, 1960 c. E. NIXON2,963,847

CORE WRAPPING METHOD AND APPARATUS FiledSept. 2,, 1954 5 Sheets-Sheet 2A l. FIG.9

INVENTOR 0564/94 619 6. N/X0/V D ATTORNEYS Dec. 13, 1960 c. E. NIXON2,963,847

CORE WRAPPING METHOD AND APPARATUS Filed Sept. 2, 1954 l4; ;0 5Sheets-Sheet 3 .ll 41 j w t u 1 E 1. Ln

II l (9' -J- a E E ATTO R N EY$ Dec. 13, 1960 c. E. NIXON 2,963,847

CORE WRAPPING METHOD AND APPARATUS Filed Sept. 2, 1954 5 Sheets-Sheet 4FIG. 5. FIG. 6.

INVENTOR 0664/?! 5 E N/)( 0/1/ ATTORNEY Dec. 13, 1960 c. E. NIXON COREWRAPPING METHOD AND APPARATUS Filed Sept. 2, 1954 5 Sheets-Sheet 5ATTORNEY United States Patent CORE WRAPPING METHOD AND APPARATUS CharlesE. Nixon, Sayville, N.Y., assignor, by mesne assignments, to InsoElectronic Products, Inc, New York, N.Y., a corporation of New JerseyFiled Sept. 2, 1954, Ser. No. 453,758

17 Claims. (Cl. 57-17) The present invention relates to method andapparatus for wrapping strips or tapes about a core to form a coveringlayer and relates more particularly to method and apparatus forhelically wrapping tapes around a core with the tension in each tapeindependently and accurately controllable and with the positions of thevarious tapes as they lie on the core precisely controllable.

The method and apparatus disclosed may be employed to Wind a coveringlayer about a conductor or textile or other type of core, but they areparticularly advantageous for use in applying tapes of easily stretchedmaterial and for thin, narrow tapes which have a low tensile strength.The method and apparatus are described as being used for helicallywrapping plastic insulation tapes of low tensile strength on anelectrical conductor to form a continuous insulation layer.

Insulating machines for wrapping insulation tapes on wire generallyoperate on the principle of feeding the wire through a servingmechanism. The serving mechanism is revolved around the wire, while thetape is fed in from an arm on the serving mechanism to the moving wireto wrap it in a helix on the wire. It is customary to use a tape supplyspool mounted on or adjacent the serving mechanism with the tape beingpayed out from the sup ply spool to the arm. The supply spool slowlyrotates with respect to the serving structure as the tape unwinds. Inorder to control the tension in the tape as it passes the arm it hasbeen customary to brake the rotation of the tape supply spool by meansof a felt brake pad or similar brake mounted on or adjacent the servingmechanism and acting between the serving mechanism and the tape supplyspool, tending to stop the slow rotation of the supply spool withrespect to the serving mechanism. Thus, in such prior machines thebraking force acts with respect to the difierential in speed of rotationof the supply spool with respect to the serving mechanism resisting thepaying out of the tape and thus tightening it up. This differentialspeed is quite low, as will be understood from the detail descriptionbelow, so that wide fluctuations in the braking force occur from momentto moment during operation, since the braking force is in effect, in anun' stable region between static and dynamic operation. Where a frictionbrake is used it tends alternately to slide and grab, sometimeschattering. Moreover, changes in effective diameter of the tape supplyspool as the tape un' winds cause other fluctuations.

In the past, insulation tapes have been made of material, such as fabricor threads, having a relatively high tensile strength. With insulationtapes of such materials this type of braking arrangement described Wasacceptable. Any fluctuations in the braking force were simply absorbedby the insulation tape, causing the insulation layer to be more tightlywound at some places on the wire than at others. These variations in thetightness of the insulation were acceptable with such materials.

The various synthetic resin tapes and other plastic tapes which are nowavailable, for example such as unfused polytetrafluorethylene, haveextremely desirable electrical insulation properties. Thus thinnerinsulation layers can now be wound on electrical conductors and yetprovide much higher voltage ratings and greatly increased ranges ofoperating temperature, resulting in considerable savings in space andweight of electrical equipment utilizing conductors insulated with thesenewer tape materials.

However, these newer materials generally have much lower tensilestrength and are far more easily stretched and damaged than any priorcommon insulation tapes.

When these newer tape materials are wound on a wire in the types ofmachines using the customary principles discussed above, the tapes areoften shredded and broken and even when not visibly damaged, the tapesare usually stretched to an extent to cause large numbers of minutevoids, which can be seen in magnification. Such voids allow thepenetration of moisture and cause low resistance leakage paths throughthe insulation, leading to break down of the equipment.

In such prior machines the problems of tape stretch and breakage areserious only a single tape of stretchable plastic is being applied to awire. When a number of these tapes are wound on at the same time, theresults have usually been the wastage of half of the wire and tape, withonly very short lengths of minimum standard insulated wire beingproduced. Moreover, the machines are subject to almost constant stoppagebecause of tape breakage.

Also, such machines are diflicult to start and stop and usually spoilthe insulation as they speed up and slow down.

Among the many advantages of the method and apparatus described arethose resulting from the fact that the tensions in the tapes as they areapplied are independently, accurately, and continuously controllableover wide ranges. The tensions in the different tapes can all be set atthe same value or each at a different value. All of the tensions,irrespective of their setting, can be gradual ly increased or decreasedtogether. Adjustments in tension can be made at any time during theoperation of the machine.

Another advantage of the apparatus described is that the tension in theconductor being insulated is readily and accurately controlled, and therate of feed of the conductor with respect to the speed of wrapping isreadily adjusted.

A further advantage is that the tension control force for every tapesupply spool is applied independently of its diflerential speed withrespect to the revolving serving structure.

Another advantage of the apparatus described is that the tension controlforce is applied as a controllable torque, whose value is independent ofspeed of rotation. With the automatic control described the apparatuscan be started from a dead stop automatically accelerated at a fast rateto at least 2000 r.p.m., held at this speed as long as desired, and thenautomatically quickly slowed back to a stop, and the entire length ofthe resulting insulated wire will have a highly desirable uniform smoothlayer of insulation material. Even when narrow tapes of unfusedpolytetrafluorethylene are used, the resulting insulated wire is of suchuniformly good quality that no visible or electrical test of theinsulation will determine which portions were produced at constant speedand which were produced during rapid changes in speed of operation.

The result is a large saving in time and materials and the production ofhundreds of feet of wire insulated with unfused polytetrafluorethylenetape or any other easily stretched tape, whereas previously onlyrelatively short lengths of such insulated wire were produced.

The various features, aspects and advantages of the present inventionwill be more fully understood from the following description consideredin conjunction with the accompanying drawings illustrating an embodimentof the present invention, in which:

Figure 1 is a perspective view of a conductor insulating machine with asmall portion shown broken away for better illustration; 7 a e V Figure2 is a skeletonized perspective view, partially diagrammatic and on anenlarged scale showing portions of the operating mechanism of themachine of Figure 1;

Figure 3 isan axial sectional view on further enlarged scale showing theturntable serving apparatus and" the tape supply spools and concentricbearing and tension control members;

Figure 4 is an axial'sectional view taken along the line 4+4 in Figure 3showing one of the guide: tube members located near the periphery of theturntable;

Figure 5 is an exploded perspective view as seen from above-showingdetails of the concentric tape spoolsupporting bearing and tensioncontrol members shown in the center of Figure 3; p

Figure 6 is an exploded perspective view of the members shown in Figure5 as seen from below;

Figure 7 is a schematic and diagrammatic drawing of the control circuitsand associated parts of the machine;

Figure 8 is an enlarged cross sectional view of one of several similarsmall ball bearing units; and I Figure 9 is a diagram for purposes ofexplanation, il-

lustrating the angular relationships between the wire and each of theinsulating tapes.

As shown in Figures 1 and 2, the bare conductor 10, is unwound from areel 12 controlled by an electric motor 14, in the base portion 16 ofthe machine. The reel is located close behind a panel door 18 with ahandle 20 so that the reel can be conveniently replaced with a full reelfrom time to time. The conductor passes successively around pulleys 22and 24 and is pulled up by a capstan wheel 25 through a hollow shaft 26rotatably supported by a pair of bearings 28. The capstan 25 issupported on'a frame 30 at the top of the machine and is driven by adrive shaft 32. 7

As shown in detail in Figure 3, a turntable serving apparatus, generallyindicated at 34, including a turntable 35 is fastened by a set screw 36near the upper end of the rotatable shaft 26. A main drive motor 38rotates the shaft 26 and turntable apparatus 34 in the direction shownby means of a V-belt 40 and'a pulley wheel 42 on the shaft 26. a 7

As the bare conductor 10 is pulled up through the serving apparatus 34,three separate insulation tapes 44, 46, and 48 are led upwardly fromthree supply spools 49, 50

and 51 through three individual tubular guide members.

52, 53 and 54 which are spaced symmetrically around the turntable 35near its rim and revolve around the conductor 10. These tapes feed inand up to a nose piece assembly, generally indicated at 56, supported ona hollow shank 57 at the center of the turntable 35. The nose pieceassembly 56 may, for example, desirably have the form shown in detailand claimed in my copending application Serial No. 453,852, filedSeptember 2, 1954, now U.S. Patent No. 2,910,821, which includes threebent pins 58'and three guide vanes 59 extending up parallel with theinsulated conductor 10', as seen in Figure 2. The shank 57 of the nosepiece assembly is held in the upper end of the shaft 26 by a set screw60. As theturntable 35 and the nose piece assembly 56 rotate each of thethree tapes is pulled around the pins 58 and then upwardly in thedirection of motion of the wire 10' and in across an inner edge of oneof the vanes 59 and then wrapped around the conductor to form a uniforminsulation layer on the conductor 10, as explained in greater detail inmy above copending application.

The insulated conductor 10 continues up past a small guide sheave 61(see Figure 1) and between another small sheave 62 on the opposite sideof the insulated wire 10' and a micrometer 63 which measures the diam- 4eter of the wire 10' as it passes the sheave 62. The wire 10' passestwice around the capstan wheel 25 and over a pulley wheel 64 on theupper frame 30 then back down through a hole 66 in the top panel 68 ofthe base 16. The insulated conductor is wound up on a reel 70 turned bya motor 14a, which is identical with the motor 14, for reasons discussedin detail below.

The capstan 25 is V driven from the main motor 38 through a speedcontrol mechanism generally indicated at 72, in Figure 2, which enablesadjustment of the relative rate at which the conductor lfi is pulledthrough the turntable 35 with respect to the speed of rotation of theturntable, to control the amount of insulation wound on a given lengthof insulated conductor 10".

As explained in detail hereinafter, automatic speed control means areprovided for the motor 38 so that both the rate of feeding of theconductor 10 and the rotational speed of the turntable 35 can becorrespondingly changed, for example in starting and stopping themachine and in regulating the production rate.

In order to enable independent control of the tension in each of thetapes 44, 46, and 48 as they feed up through their respective guidetubes and in to the nose piece assembly 56, the tapes 44, 46, and 48 arepayed out from three independently rotatable tape supply spools 49, 50and 51, respectively, which'are concentric with each other and with theshaft 26.

As shown most clearly in Figure 3, each of these tape supply spools issecured to an individual bearing and tension control member 74, 76, or78, respectively. These control members are concentric with eachotherand with the shaft 26 and the conductor 15!. Each control member 74, 76,or 78 is freely rotatable with respect to the shaft 26 and with respectto the serving mechanism 34.

In order to control the tension in each of the tapes 44,

46, and 48 as they payout from the supply spools to their respectiveguide members 52, 53, and 54, grooved flanges 80, 82, and 84 areprovided at the lower ends of the members 74, 76 and 78, respectively.Three small round belts 86, 88, and each connect respective ones ofthese control members 74, 76 or 78 to a small electric motor 92, 94, or96. When the machine is in operation these motors are used as generatorsto place a constant braking torque on the spools 49, 5t) and 51, asexplained in detail hereinafter. Referring to the spool 49 and itscontrol member 74 in greater detail, the spool 49 may be formed of atransparent plastic material, such as Plexiglas with a hub portion and apair of wide flanges spaced apart slightly farther than the width of thetape. The hub is fastened to the top, end of the cylindrical metal bodyof the control member 74 which has a bore :of slightly larger diameterthan the outside of the shaft 26. Three small ball bearing units 104 areequally spaced around the top and bottom ends of the cylinder 100, androtatably support the member 74 around the shaft 26.

Each ball bearing unit includes an inner race held by a machine screw166 onto the cylinder 180 and anouter race whose rim runs on the outersurface of the shaft 26. The lower end of the cylinder 100. has theflange 80 with a groove 108 engaging the belt 86. p

In order to support the bearing and control members 74, 76, and 78, onthe shaft 26, .a conical bearing surface 110 is provided on the rim 89adjacent the groove 108. A collar 112 held by four'set screws 114 on theshaft 2'5 has three larger ball bearing units 116 mounted at an angle torun on the bearing surface 110'. c

The spool 50 is similar to the spool 49 with its. hub portion fastenedto the upper end of the cylindrical body 118 of, the control member 76'which has a bore 128 slightly larger than the outside. of the cylinder109, as seen in Figure 3.

Six equally spaced slots 122 (see Figure 5) are cut in the top ofthecylinder 118 to carry six ball bearing units 124 and 126 in alternateinner and outer positions and all similar to the units 104 and similarlyheld by machine screws 106. The three units 124 have their rimsprojecting slightly into the bore so as to run on the outer surface ofthe cylinder 100; whereas the three alternate units 126 have their rimsprojecting beyond the outer surface of the cylinder 11-5 to support theupper end of the control member 78 around the cylinder 118, as seen bestin Figure 3.

At the lower end of the cylinder 118, as seen in Figure 6, are threemore ball bearing units 124 with their rims projecting slightly into thebore 120 to roll on the outer surface of the cylinder 100. An annularrecess 127 is formed in the upper surface of the flange 80 to provideclearance for the three lower bearing units 124. Three equally spacedslots 12S carry three more ball bearing units 126 with their rimsextending out beyond the outer surface of the cylinder 118 and above theflange 82 so as to support the lower end of the outer control member 78around the cylinder 118, as seen in Figure 3.

The lower end of the cylinder 118 has the flange 82 with a groove 130engaging the belt 88. A conical bearing surface 132 is provided on theflange 82 to engage three ball bearing units 134 secured at equallyspaced points around the flange 80 thus supporting the control members76 and 78. These bearing units 134 may also be similar to the units 104.

The spool 51 is generally similar to the spools 49 and 50 and isfastened to the upper end of the cylindrical portion 136 of the controlmember 78. At the lower end of the cylinder 136 is the flange 84 with agroove 137 engaging the tape tension control belt 90. A conical bearingsurface 138 is provided at the lower end of the cylinder 136 to ride onthree ball bearing units 140 equally spaced around the upper surface ofthe flange 82. The ball bearing units 140 may be generally similar tothe units 104 described above.

With this bearing arrangement as described, all of the supply spools 49,50 and 51, are independently rotatably supported in concentricrelationship with the shaft 26. Moreover, the belts 86, 88 and 90running in their respective grooves on the flanges at the lower ends ofthe control members 74, 76 and 78 provide easy means for applying thedesired amount of torque to these control members to tension the tapes44, 46 and 48 as they pay out from the supply spools 49, 50 and 51. Thebelts 86, 88 and 90 run around small pulley wheels 142, 143, and 144 onthe shfits of the small motors 92, 94 and 96, respectively. These beltsare held taut by spring biased pulley wheels 148.

Another advantage of the arrangement of the bearings is that the conicalsurfaces 110, 132 and 138 are arranged at a 45 angle, which helps toposition accurately the control members 74, 76 and 78 in concentricrelationship with each other.

A further advantage of the independent concentric arrangement of thetape supply spools and their control members is that the motions of thevarious spools is not directly compared to the turntable speed by anycoupling mechanism such as the tension control brakes used in priormachines, as described above.

Among the advantages of using the small individual bearing units 104,124, 126, 134 and 140 is that any friction is very eflectivelyminimized. These bearing units (see Figure 8) have their small balls 139located in races closely adjacent the central hole 105 for the machinescrew 106, and the relatively larger diameter of the outer rim 141 ofthe ball bearing units provides considerable leverage for the rollingsurfaces, further minimizing any slight friction effects due to rollingfriction of the balls 139.

With the construction shown I have found that the supply spools 49, 50,51, all operate substantially without any frictional drag upon eachother, for example, even when operating in different directions atdifferent rates of speed. It is to be understood that other antifrictionbearing arrangements may be used in order to allow all of the tapesupply spools 49, 50, and 51 and the control members 74, 76 and 78 torotate independently of each other and of the turntable and yet toenable independent control of the rotation of each spool.

In Figure 9 is shown a diagram which will be used in connection with adiscussion of the differential in speed between the turntable 35 and thesupply spools 49, 50 and 51. This diagram relates the mean distance Daround the conductor 10 which is covered by any one of the insu lationtapes during one revolution of the turntable serving apparatus, with thelength L of the conductor 10 which passes through the head assembly 56during one revolution of the turntable 35, with the total un-overlappedwidth W of tape wound onto the conductor during each revolution of theturntable and with the amount A of tape which is helically wrapped onthe conductor during each revolution of the turntable 35. I

For example, assume that the conductor 10 has a diameter of 60 mils andthat each of the tapes 44, 46 and 48 of unfused polytetrafluorethyleneis 4 mils thick and is 716 of an inch in width. Also assume that eachtape is being wound on the conductor 10 so that approximately two-thirdsof each tape overlaps one or both of the preceding tapes as shown in mycopending application, identified above. This makes the insulation 12mils thick before fusing. Thus, the mean distance D around the conductoris 7211 mils or 226 mils. The sum of the un-overlapped tape widths is fiof an inch or 187 mils. The angle 0 at which the tape is Wound withrespect to the axis of the conductor 10 is cos- (187/226)=34.1. Thelength L is thus 226 ctn (34.l)=334 mils, and the amount A of each tapewound on the conductor during each revolution is 226/sin 34.1:403 mils.

With the precise control provided by the present method and apparatus,there is substantially no stretch in the tapes 44, 46 and 48. Thus,approximately 403 mils of tape pays out from each spool during eachrotation of the turntable.

Assuming that the machine is operating at 1000 r.p.m., and that each ofthe spools 49, 50 and 51 has an over-all diameter of 10 inches and isfull, then each of the spools is rotated by about .0128 of a turn foreach revolution of the turntable 35. Thus, the spools 49, 50 and 51, are

rotating at about 12.8 r.p.m. with respect to the turntable 35.Depending upon the direction in which the tapes were wound on thespools, they either travel 12.8 r.p.m. faster or slower than theturntable 35. In the machine, as shown, the spools 49, 50 and 51 travelfaster than the turntable at 1012.8 r.p.m. with respect to the machineframe.

As the tapes unwind, the effective diameter of the rolls of tape in thespools 49, 50 and 51 decreases and so their differential in speedincreases. For example, assuming that the diameter of the hubs of thespools is 4 inches,

then when they are almost unwound the difierential in speed rises to 32r.p.m. This is a 250% change in the differential speed.

On the other hand, the absolute speed has risen only to 1032 r.p.m. withrespect to the machine frame, a 1.9%

unwinding of the tape.

In prior machines which apply the braking force between the revolvingserving apparatus itself and the tape supply spool, the low difierentialspeed sometimes causes the braking apparatus periodically to stick andthen jump,

causing wide tension variations. It is seen that in prior machinesthetension is also subject to large, variations due to the unwinding ofthe spool and the consequent large amountofincrease in difierentialspeed which in addition,maycausechanges in the running character-'istics.

Moreover, the reduction in the effective diameter of rolls of tape onthe supply spools as it unwinds has the efiect of reducing the leveragearms of the taps in turning the spools 49, 50 and 51 about their axes.In the example discussed above the leverage arm drops to .4 of itsinitial value. The result in prior machines is a further increase in thetensions to which the tapes are subjected.

' In the present machine, this same change in leverage arm takes-place,but it occurs without any substantial change in thespeed of rotations ofthe spools with respect to the external tension controlling motors 92,94 and 96. Moreover, an advantage of the method and apparatus disclosedherein is that the'tension control operates in such a way that thischange in leverage has no significant effects, or it may be compensatedfor simply by changing the constant torque-braking force applied by themotors 92, 94 and 96 through the belts 86, 88 and 90.

To accommodate the different heights of the supply spools 49, 50 and 51,the tubular guide members 52,53 and 54 project down different distancesbelow the turntable 35, as indicated in phantom in Figure 3. The lowerends of these tubular guides are cut off at an angle of 45 to provideclearance for the tapes to enter. Each guide. includes lower and upperrollers 145 and 146, with the axes. of each lower roller 145 turnedslightly so as to face it in the direction from which the tape pays outfrom the respective tape supply spools when they are about half full,i.e. to face the mean radius of the tape winding. The upper rollers 146are'held in short sleeves 147 and can be turned at any desired anglewith respect to the turntable 35, depending upon the shape of the nosepiece assembly 56 being used and the relative positions of the pins 58..

Another advantage of the arrangement disclosed is that the controlmotors 92, 94 and 96 are used to turn the tape spools to wind them up.As illustrated diagrammatically on reduced scale at the right in Figure3, a bobbin 148 of newtape is placed on one of the three pins 150 nearone side of the top panel of the machine and the tape is wound onto thecorresponding spool. All three spools can be wound at once by usingthree bobbinsg'each bobbin is preferably held at adifierent height.

The power for driving the capstan wheel- 25 is coupled from anadjustablepulley 151 on the lower end of the shaft of the main motor 38, through aV-belt 152 to a pulley 154 on a shaft 156 carried on a carriage 158slidingly supported on apair of rods 160 secured to the frame of themachine.

In order to slow the speed of the capstan wheel 25 with respect to theturntable 35, a hand wheel 162 on the front of the machine is turnedclockwise, rotating a screw 164 and moving the carriage 158 along therods 160 toward the hand wheel 162. The belt 152 becomes tightened andslides down deeper into the adjustable pulley 151, thus reducing theeffective diameter of this pulley. At the same time, the motion of thecarriage moves, another adjustable pulley 166 on the upper end of theshaft 156 further from a pulley 168 on the lower end of the shaft 32,tightening up a V-belt 170 extending between them and causing it toslide down further into the adjustable pulley 166, reducing itselfective diameter. Thus, the unit 72 reduces the effective diameters ofeach of the driving pulleys 151 and 166 with. respect to the drivenpulleys 154- and 168, respectively and thus slows down the'shaft 3'2with respect to the turntable. As shown in Figure 1 the top end of theshaft 32 carries a cone gear 168 engaging another cone gear 170connected to a worm-drive speed reducing unit 172 coupled to the shaftof the capstan wheel 25.

Turning the hand wheel 162 in the opposite direction enlargestheefiective diameters of the respective driving pulley 151 and 166 andthus speeds up the capstan wheel 25 with respect to the speed of theturntable 35.

Shown within the outlined area 174' at the lower left of Figure 7 is theautomatic speed change mechanism for the machine as a whole. Thisincludes '2: Ward- Leonard motor-generator system with an inductionmotor 176 connected by leads 178' to a pair of alternating current powerlines 180 on the machine. The motor 176 is connected by a shaft with adirect current generator 182 connected by leads 184 to the main drivemotor 38 which is a DC. motor. The field winding 186 of the generator182 is energized from the lines 180 through a bridge" rectifier 188having its output connected across a potentiometer 190. One end of 'thefield 186 is connected to one side of the potentiometer 190 and theother side is. connected to a movable contact 192 on the potentiometer.A reversible series A.C. motor 194 is connected through a worm-gearspeed reducing unit 196 to the movable contact 192. The motor 194 hasits field 198 and armature connected to the A.C. lines 180 through adouble-pole double-throw reversing switch 200 shown at the right of theinstrument panel of the machine adjacent an indicator 202 which showsthe r.p.m. of the main drive motor 38' and also by a suitable conversionfactor shows the speed of the turntable 35. When the switch 200 isthrown to its Fast position (the up position in Figure l), the motor 194drives the movable contact 192 slowly around the rheostat 190 so as toincrease the voltage applied to the field winding 186 of the generator182'. The gear ratio in the unit 196 is such that it takes about oneminute for the movable contact 192 to move from the left end of therheostat 190 to the right end, speeding up the motor 38 so as toaccelerate the turntable from zero to about 2,000 r.p.m. Throwing theswitch 200 to its slow position gradually slows down the machine. Thespeed indicator 202 can be a voltmeter movement connected to a smallD.C. generator 203 mounted on the panel 68' (see Figure l) driven by themotor shaft and arranged to have an output voltage which linearlyincreases with speed.

In order to control the tension throughout the length of the conductor10 between the reels 12 and 70, the identical D.C. shunt motors 14 and14a are used with their field windings 204 and 204a, respectivelyconnected in parallel by leads 206 and energized from a bridge rectifier208 connected to 'the A.C. lines 180. Thus, full rated DC. voltage iscontinuously applied to both of the fields 204 and 20411 when themachine is on. The arma- .turcs of these meters 14 and 14a are connectedin series by a lead 210 and are both connected across a bridge rectifier212 by the leads 214 and 216. The bridge rectifier '212'is energized byan adjustable A.C. voltage from a variable reactor 217 having a slidingcontact 218', adjustable by a conduct'ortension control knob 219 at therear of the top panel. 68.

The motors 14 and 14a are both arranged to drive their respective reels12 and 70 in such directions that they both tend to wind up theconductor 10 and thus tension it between the reels 12 and 70. The amountof tension is quickly and easily adjusted by moving the contact 218 ofthe variable voltage control 217' so as to change the armature currentsin these motors. Since the motors 14. and 14a are identical, the opposedforces on opposite ends of the conductor 10 are always substantiallyequal, irrespective of the motion of the conductor 10, and thus thetensions along the conductor are the same at all points varying onlywith changes in the diameter of the wire wound on the reels 12 and 70.

The capstan wheel 25' is subjected to no net force from the motors 14and 14a irrespective of the speed or tension of the conductor. Thisarrangement has proven quite advantageous, for it enables independentadjustments of the conductor tension and of the capstan speed, regulated9, by the unit 72, and also assures uniform tension all along the lengthof the conductor 10.

In order to regulate the tape tension controlling motors 92, 94 and 96,the circuits at the right of Figure 7 are provided. The individualbranch circuits I, II and III for these three motors are identical, andso corresponding parts are indicated by the same reference numeral. Whenthese motors are being used to control the tensions in the three tapes,they are connected as generators by means of their respective four-poledouble-throw switches 230, which are thrown into the left or TensionPosition. In the Tension Position, the field windings 232 are connectedthrough individual tape tension equalization potentiometers 234 to apair of leads 236 connected to the Tension Position contacts of adouble-pole doublethrow master switch 238. The movable contacts 239 ofthe potentiometers 234 are adjusted by the respective control knobs 240adjacent the motors 92, 94, and 96 on the top panel 68. With the masterswitch 238 in its Tension Position, the leads 236 are connected across avoltmeter 242 at the left of the instrument panel of the machine to theoutput of another bridge rectifier 244, which is energized from avariable reactor 245. This variable reactor is connected from thesecondary 246 of step-down transformer 248 having its primary 250connected to the AC. lines 180. The movable contact 252 of the variablevoltage control 245 is adjusted by the knob 254 on the instrument panelto regulate the D.C. voltage available on the leads 236 as indicated bythe meter 242, thus regulating the currents in the field windings 232,and hence regulating the amount of field flux in the motors 92, 94 and96 and so the torque required to turn their armatures when they areoperating as generators.

During operation at the normal turntable speed of about 1,000 r.p.m.,the armatures 256 of the motors 92, 94 and 96 are driven at a fairlyhigh rate of speed by the belts 86, 88 and 90. Each of these armaturesis connected through an ammeter 258 and through the switch 230 to avariable load resistor 260, which is used as an individual tape tensioncontrol. The movable contacts of the variable resistors 260 are adjustedby the control knobs 262 on the instrument panel beneath the dials ofthe respective ammeters 258; The current generated by the armatures 256is dissipated in the variable load resistors 260, thus causing a brakingtorque to be exerted by the pulley wheels 142, 143 and 144 on therespective belts 86, 88 and 90.

In adjusting the machine for the operation of wrapping a core, theindividual tape tension equalization knobs 240 are adjusted so that thevoltages applied to the individual fields 232 produce equal currents inthe armatures 256 when the individual tape tension control knobs 262have identical settings. Once the knobs 240 have been adjusted, anyslight actual differences in characteristics of the motors 92, 94, and96 are compensated for, and usually the knobs 240 need not be adjustedagain. With the motors 92, 94 and 96 all equalized for generator action,the magnitudes of the currents through the meters 258 is an accuratemeasure of the torque being applied by these motors to the respectivecontrol members 74, 76 and 78. The individual tape tensions can be setat a wide range of different values, as may be desired, by adjusting theindividual load resistors 260. All of these tensions can besimultaneously increased or decreased by varying the amount of fieldvoltage by using the knob 254 on the master tape tension control 245.

Among the many advantages of this arrangement is that the motors 92, 94and 96 when used as generators provide an easily adjusted constanttorque, which is a linear function of speed, being the combined resultof the field flux in the motors and of the respective armature currents.The field flux is adjusted by the setting of the contact 252, while thearmature current is a function of generated E.M.F., which isproportional to speed.

In order to rewind the spools 49, 50 and 51, the individual switches 230and the master switch 238 are thrown to the Rewind Position (the rightposition in Figure 7 or the rear position as seen in Figure 1). Thisenergizes the field windings 232 with fixed D.C. voltage through leads263 from a bridge rectifier 264 connected to the secondary 246. In therewind position, the armatures are connected to the leads 236 so thatthe applied voltage and hence their speeds of rewind can be adjusted bythe knob 254, as desired. In rewind operation, the master tape tensioncontrol 245 becomes a master rewind speed control, and thepotentiometers 234 may act as individual speed controls if desired.

I have found that small D.C. shunt motors, for example such as thosemade by John Oster Manufacturing Corporation of Genoa, Illinois, TypeBT-2-l5, having a rating of 28 volts, 1.1 amperes, and providing 1ounceinch of torque are well suited to provide the braking torquedesired on the control members 74, 76 and 78. By selecting the ratios ofthe diameters of the pulleys 142, 143 and 144 on the motor shafts andthe diameters of the grooves in the flanges of the control members 74,76 and 78, the motors 92, 94 and 96 can be arranged to provide 1ounce-inch of torque on the tape spools when the spools are half full.Thus, the ammeters 258 may be read directly in ounce-inches of brakingtorque as a function of amperes.

Other braking torque devices can be used, for example such as eddycurrent brakes of the kind found in wattmeters, but provided withelectromagnets instead of fixed magnets to enable adjustment or providedwith viscosity friction braking devices, or the like. However, I findthat the motor-generator type of tension control unit, such as the Ostermotors described, are quite satisfactory for most applications for theyhave the additional advantage of providing an easy means of rewindingthe tape spools. When desired a small portable electric motor with arubber-tired wheel on its shaft that can be held against the flanges ofthe supply spools is used to wind on the tape.

The power for the machine is supplied from 60 cycle AC. power mains 270through a main switch 272 associated with a pair of fuses 274 and asuitable on-off indicator lamp '276 connected across the lines in themachine.

In the method of the present invention, as embodied in the machinedescribed, the core to be wrapped is fed along a path, and the strip orstrips to be wrapped on the core are unwound from a concentricrelationship with this path and are fed out to points spaced from thepath and revolving around the path of the core and are then fed back intoward the path and are helically wrapped around the core, while abraking torque independent of the motion of the revolving points isapplied to the strip or strips as they are in their concentricrelationship with respect to the path of the core.

More broadly the method of the present invention includes the steps offeeding a core to be wrapped along a path, feeding the strip to bewrapped on the core to a point which is spaced from the path and whichis revolving around the path and applying a tension force to the stripbefore it reaches said point this tension force being independent of themotion of said point, and feeding the strip in to said path and wrappingit helically on the core.

From the foregoing description it will be understood that the presentinvention is well adapted to accomplish the ends and objects set forthand to provide the advantages described and that the method andapparatus of the invention may be subject to various modifications eachas may best suit the method and apparatus to a particular applicationand that the scope of my invention includes such modifications.

I claim:

l. The method of helically wrapping a plurality of strips around a'core,comprising the steps: of feeding .the core along, a path fixed invposition with respect to' a fixedv and stationary referenceelemeut,providing supply spools of'equaldiameter in concentric relationship withsaid path for supplying said strips, unwinding the strips fromrespective ones of said: spools. in concentric relationship with saidpath, feeding the strips out to points. spaced from said path andrevolvin'g'around said path, feeding the strips from said points in tothe path, wrapping the strips around the core, and applying individualcontrolling torques to. eachxof the spools as the strips unwind fromtheir concentric relationship with said path, said controlling torquesbeing applied directly from torque exterting means mounted on said fixedand stationary reference element to each of said spools to control therate of rotationof each of said spools with respect to its torqueexerting means.

2; Apparatusffor helically wrapping a core with a tape comprising afixed and stationary machine frame, means on said fixed andstationaryframe defining a path for said core, core tensioning andmoving means for tensioning said core in said 'path and moving it alongsaid path, a first tape guide spaced out from said path and mounted onsaid fixed and stationary frame to revolve around said path, revolvingdrive means coupled to said first guide for revolving it around saidpath, a second tape guide closely adjacent said path, a tape supplyspool rotatably mounted on said fixed and stationary frame concentricwith said'path to rotate independently of the motion of said firstguide, the tape on' said spool unwinding and paying out to said firstguide and from. said first guide to said second guide and then beingwrapped around said core in said path, and an adjustable tape tensioningmechanism having stationary and rotating portions, said stationaryportion being rigidly secured to said fixed and stationary frame andsaid rotating portion being coupled to said'spool, said tape tensioningmechanism applying torque to said spool to tension said tape as it paysout from said spool' 3. Apparatus for wrapping a conductor with aplural,- ity of tapes comprising a machine frame, means on said framedefining a'path for said core, core 'tensioning and moving means fortensioning said core in said path and moving it along said path, astructure rotatably mounted on said frame to rotate concentric with saidpath, a plurality of first tape guides on said structure and spaced outfrom said path to revolve around said path, drive means for rotatingsaid structure, a second tape guide with portions spaced around saidpath, a plurality of tape supply spools rotatably mounted on saidmachine frame, each of said spools rotatable independently of any otherspool and independently of said structure and each being adapted tocarry at least one tape, said spools being arranged to pay out the tapesto respective ones of said first guides, said first guides beingarranged to feed the tapes to said second guide and to Wrap the tapesaround the core, and a plurality of controllable torque-exertingdevices'mounted on said frame and each coupled to one of said spools.

4. Apparatus for wrapping tapes around a core comprising a machineframe, a hollow drive shaft rotatably supported on said frame, drivemeans connected to rotate said shaft, core tensioning and feeding meansfor feeding the core along a path through said drive shaft, a pluralityof tape guiding members secured to said shaft and spaced out from saidpath to revolve around said path as the shaft is rotated, a plurality oftape supply spools concentric with said shaft, bearing means supportingeach of said spools to rotate freely with respect to said shaft and withrespect to said guiding members, a plurality of electric motors on saidframe each coupled to one of said spools, and a plurality of controlsfor regulating the current in said motors to regulate the tension ineach of said tapes as they pay out from their respective spools.

' 5. Apparatus for wrapping, tapes around a core com- 12 prising amachineframe, a hollow drive shaft rotatably supported on said frame,drive means connected to rotate said shaft, core; tensioning andfeeding" meansfor feeding. the core along arpaththrough said driveshaft, a plurality. of tape guiding'ielements secured to said shaft andspaced" outfrorn: said path to. revolve around said path as. the shaftisirotated, a pluralityjof; tape supply spoolsarranged side by side, andconcentric with said shaft and each freely rotatable. with respect to.each other and with nespect to said shaft,a plurality of spoolcontrolmemprising a machine frame, a hollow drive shaft rotatablysupported on said frame, drive means connected to rotate said shaft,core tensioning and feeding means for feeding the core along apath'through said drive shaft, a plu rality of'tape guiding elementssecured to said shaft and spaced out from. said path to revolve aroundsaid path as the shaft is rotated, a plurality of'tape supply spoolsarranged side. by sidev and concentric with said shaft and each freelyrotatable with respect to each other and with respect to said shaft, aplurality of cylindrical spool control memberseachi concentric with saidshaft and with each other and having first and second respective ends,the inner memberbeing longe'st'and' having its first end connected to anend spool, successive outer members being progressively shorter, eachsuccessive outer memher having its firstend connected to a spoolsuccessively farther from. said end spool, and a plurality of torqueexerting devices each coupled between said frame and one ofthe secondends of said members.

[Apparatus for wrapping tapes around a core as claimedin claim 6 andwherein said torque-exerting devices are electric motors each mounted onthe frame and having its rotor connected to. the second end of one ofsaid control members.

8. Apparatus for wrapping tapes around a core as claimed in claim 7 andwherein the second end of each successive outer control member isshorter than the second end of the next inner member, and the secondends of all of said members having pulley. grooves and the rotors ofrespect-iveones of said electric motors are con nected by'belts to saidgrooves. f

9. Apparatus for helically wrapping a tape around a core comprising amachine frame, tape serving mechanism revolvably mounted on the frame,drive means for revolving said mechanism, first and second electricmotors each'havingfield and armature windings, first and second corereels respectively coupled thereto, said core being arranged to unwindfrom said first reel, to pass along a' path through said servingmechanism and to wind up on said second reel, a capstan arranged to movesaid core along said path, first circuit means connecting said' fieldwindings together, current source means connected to said first circuitmeans equally to energize said field windings, second circuit meansconnecting said annature windings together, current source means'connected to' said second circuit means equally to energize said armaturewindingslto urge both of said reels in directions such as to tend r windup said core, and a current control arranged to regulate the currentfrom one of said current sources to one of said circuit means toregulate the'tension insaid core. 5

10. Apparatus as claimed in claim 9 and wherein said second circuitmeans connectszsaid armature windings in series and said current controlregulates the. current through bothofi said armature windings.

1.1. Apparatus. for wrapping tape. around. a core comprising a machineframe, tape serving mechanism revolvably mounted on said frame,'a maindrive motor for revolving said serving mechanism, core guiding meansdefining a path through said serving mechanism, a core driving wheel,for moving a core along said path, an adjustable speed control powertransmission mechanism coupling said Wheel to said main dnive motor,whereby said wheel is driven by said main motor and the speed ratiobetween said tape serving mechanism and said core driving wheel can beadjusted, and a master speed control connected to said main drive motorfor simultaneously controlling the speeds of said tape serving mechanismand said core driving wheel.

12. Apparatus as claimed in claim 11 and wherein said master speedcontrol includes a movable element which can be moved through a range ofpositions and is arranged to produce a corresponding range in speeds ofsaid main drive motor, and a reversible motor connected to said elementto move it in either direction through said range of positions.

13. Apparatus for wrapping insulation tapes around a conductorcomprising a machine frame, a vertical hollow drive shaft rotatablysupported on said frame, drive means coupled to said shaft to rotate it,a turntable secured to said shaft near its upper end, a plurality oftape guiding elements on said turntable near its edge each adapted toguide a tape from below to above said turntable, a plurality of tapesupply spools arranged horizontally side by side below said turntableand concentric with said shaft, a plurality of cylindrical spool controlmembers concentric with said shaft and telescoped within one another,each successive inner member projecting above and below the memberstherearound, the hub of the top spool being secured near the upper endof the inner member, the hubs of successively lower spools being securednear the upper ends of successive outer members, an abutment on saidshaft below the inner member, low friction bearing means between saidabutment and the lower end of said inner member and between said shaftand the inside of said member, a flange on the lower end of each memberwhich is surrounded by another member, low friction bearing meansbetween each of said flanges and the next outer member and between theoutside of each member and the inside of the next member, whereby all ofsaid members and their respective spools are freely rotatable about saidshaft with respect to each other, and a plurality of controllableelectric motors on said frame coupled to said flanges.

14. Apparatus for wrapping insulation tape around a conductor comprisinga machine frame, tape serving mechanism revolvably mounted on saidframe, a main drive direct current motor, a first drive connectionbetween said motor and said serving mechanism for revol ing said servingmechanism, means defining a path for said conductor through said servingmechanism, a capstan wheel adapted to engage a conductor in said path, asecond drive connection between said wheel and said motor for movingsaid conductor along a path, a source of alternating current, analternating current motor connected thereto, a DO. generator having itsarmature mechanically connected to the rotor of said AC. motor and beingelectrically connected to said main motor, a source of direct current, arheostat, the field of said generator being connected to said sourcethrough said rheostat, and a reversible motor connected to said rheostatand arranged to vary its resistance to change the speed of said mainmotor.

15. Apparatus for helically wrapping a plurality of insulation tapesaround an electrical conductor while accurately controlling the tensionin each tape comprising a machine frame, means on the machine framedefining a path for the conductor, tensioning and driving mechanism formoving the conductor along said path, a plurality of revolving tapesupply spools concentric with said path, a revolving serving mechanismconcentric with said path and having a plurality of tape-guidingelements spaced from said path, revolving drive mechanism for revolvingsaid serving mechanism, the tape from each of said spools being adaptedto unwind from its spool, pass its respective tape-guiding element, andthen to approach said path and wind around the electrical conductorpassing therealong as the serving mechanism is revolved, and tapetension controlling mechanism for each of said spools including arevolving member coupled to each spool and revolving therewith and amember fixed on the machine frame co-operating with said revolvingmembers for applying accurate tension controlling torques between thefixed machine frame and each of said revolving spools.

16. Apparatus for wrapping a plurality of insulation tapes around anelectrical conductor while accurately controlling the tension in eachtape comprising a machine frame, conductor supporting means on themachine frame supporting the conductor for movement along a path throughthe machine, a plurality of revolving tape supplies concentric with thepath of the conductor, said tape supplies being revolvably supported forrevolution independently one from another, a revolving serving mechanismconcentric with said path and including a plu rality of tape-guidingelements spaced from said path, revolving drive mechanism for revolvingsaid serving mechanism, said tape supplies being revolvably supportedfor revolution independently of the serving mechanism, the tape beingadapted to unwind from each of said supplies and to pass its respectiverevolving tape-guiding element and then to approach said path and windaround the electrical conductor passing along said path as the servingmechanism is revolved, and tape-tension-controlling mechanism for eachof said tapes including a member coupled to each of said tape suppliesand revolving therewith, a stationary member, and adjustabletorquecontrolling means operatively associated with said stationarymember and said revolving members for applying accuratetension-controlling torques between the fixed machine frame and each ofsaid revolving tape supplies.

17. Apparatus for helically wrapping a plurality of insulation tapesaround an electrical conductor while accurately controlling the tensionin each tape comprising a fixed and stationary machine frame,conductorguiding means on the machine frame adapted to guide theconductor along a path through the machine, a revolving servingmechanism concentric with said path and having a plurality oftape-guiding elements spaced from said path, revolving drive mechanismfor revolving said serving mechanism, a plurality of tape supply spoolsof the same diameter adapted to have tape wound thereon concentric withsaid path, each of said tape supply spools being rotatably supported forrotation independent one from another and independent of the movement ofsaid serving mechanism, the tape from each of said spools being adaptedto unwind from its spool and to be guided by its respective tape-guidingelement so as to wind around the electrical conductor passing along saidpath as the serving mechanism is revolved, and tape tension controllingmechanism for each of said spools including a member held stationarywith respect to the fixed and stationary machine frame, andtension-controlling torque-exerting means acting from said stationarymember to each of said tape supply spools for providing accuratetension-controlling torques individually to each of said tape supplyspools, said torque-exerting means being operatively interposed betweensaid stationary member and each of said tape supply spools forcontrolling the rate of rotation of each of said spools with respect tosaid stationary member, whereby the tension of each tape is accuratelycontrolled as it unwinds from its spool and winds around the electricalconductor.

(References on following page) Refe l enges Cited in the, file of thispatent UNITED STATES PATENTS Kruesi et a1. Jan. 19, 1886 16? EampnQ- t;a1 '.'.,,June, 4, 19.35 Henning'et a1. -7 Aug. 10, 19,43v Bouge t De 28,19 48 Bouget L. Feb. 22, 1949 Spillmap 1, 1949 Olson et a1. Feb. '19 1957

